tl;dr: Tarsney slightly misrepresents an existential risk estimate.
Tarsney writes:
To my knowledge, the most pessimistic estimate of near-term existential risk in the academic literature belongs to Rees (2003), who gives a 0.5 probability that humanity will not survive the next century.
But what Rees actually writes is:
I think the odds are no better than fifty-fifty that our present civilisation on Earth will survive to the end of the present century.
(Here’s one online source quoting Rees. I’ve seen the same quote elsewhere too.)
Whether “our present civilisation on Earth” survives is very different from whether humanity survives. I haven’t read Rees’ book, so I don’t know what he intended that quote to mean, but I’d guess he’d include things like a major population collapse that lasts a few decades as “our present civilisation on Earth not surviving”. Arguably, his forecast could even be seen as capturing the chance that we just very substantially change our political, cultural, and economic systems, in the same way as how Europe in the 1900s was arguably a “different civilisation” to Europe in the year 100CE.
Also, Rees doesn’t give a 0.5 probability; he gives a probability no better than 0.5.
For a collection of such estimates, see Tonn and Stiefel (2014, pp. 134–5).
I think it’d be better to direct people to the appendix of Beard et al. (2020), since that’s more comprehensive and up-to-date. (I also really like the article itself.)
Perhaps unsurprisingly, I also think it’d be even better-er to direct people to my database, since that’s even more comprehensive and up-to-date (and people can and do make suggestions to it, which I process, such that it should presumably remain the most comprehensive resource, rather than being frozen in time). But I can understand Tarsney preferring to refer readers to an academic source.
(Incidentally, if there’s anyone who’d in theory like to cite my database, but can’t do so unless it’s hosted somewhere else—e.g., a preprint server—or needs it to look different, please let me know and I’ll see what I can do.)
Tipler doesn’t give a quantitative estimate, so maybe that shouldn’t count.
Leslie and Bostrom’s estimates themselves are arguably less pessimistic than Rees, in the sense that their lower bounds for the risk level are lower
But I include their estimates here anyway since it’s possible that their overall distribution would be more pessimistic, and because Rees’ estimate is not necessarily about existential catastrophe (since it could include other ways in which “our present civilisation” doesn’t “survive”)
Leslie and Bostrom’s estimates aren’t as near-term as Rees’ estimate
So Tarsney’s claim is reasonable on this front; I’m just adding some extra info.
There are also some more pessimistic estimates in sources that aren’t academic but do seem similarly worth paying attention to to Rees’ estimate; see my database.
tl;dr: Tarsney slightly misrepresents an existential risk estimate.
Tarsney writes:
But what Rees actually writes is:
(Here’s one online source quoting Rees. I’ve seen the same quote elsewhere too.)
Whether “our present civilisation on Earth” survives is very different from whether humanity survives. I haven’t read Rees’ book, so I don’t know what he intended that quote to mean, but I’d guess he’d include things like a major population collapse that lasts a few decades as “our present civilisation on Earth not surviving”. Arguably, his forecast could even be seen as capturing the chance that we just very substantially change our political, cultural, and economic systems, in the same way as how Europe in the 1900s was arguably a “different civilisation” to Europe in the year 100CE.
Also, Rees doesn’t give a 0.5 probability; he gives a probability no better than 0.5.
Also, Tarsney writes:
I think it’d be better to direct people to the appendix of Beard et al. (2020), since that’s more comprehensive and up-to-date. (I also really like the article itself.)
Perhaps unsurprisingly, I also think it’d be even better-er to direct people to my database, since that’s even more comprehensive and up-to-date (and people can and do make suggestions to it, which I process, such that it should presumably remain the most comprehensive resource, rather than being frozen in time). But I can understand Tarsney preferring to refer readers to an academic source.
(Incidentally, if there’s anyone who’d in theory like to cite my database, but can’t do so unless it’s hosted somewhere else—e.g., a preprint server—or needs it to look different, please let me know and I’ll see what I can do.)
tl;dr I’m aware of 1-3 other things that might count as more pessimistic estimates of near-term existential risk in the academic literature.
Specifically:
Frank Tipler wrote “Personally, I now think we humans will be wiped out this century”
John Leslie estimated the risk of extinction over the next five centuries as at or above 30%.
Nick Bostrom estimates the odds that “existential disaster will do us in” at some point as probably at or above 25%.
For further details and sources, see my Database of existential risk estimates (or similar) (see here for the accompanying post).
But:
Tipler doesn’t give a quantitative estimate, so maybe that shouldn’t count.
Leslie and Bostrom’s estimates themselves are arguably less pessimistic than Rees, in the sense that their lower bounds for the risk level are lower
But I include their estimates here anyway since it’s possible that their overall distribution would be more pessimistic, and because Rees’ estimate is not necessarily about existential catastrophe (since it could include other ways in which “our present civilisation” doesn’t “survive”)
Leslie and Bostrom’s estimates aren’t as near-term as Rees’ estimate
So Tarsney’s claim is reasonable on this front; I’m just adding some extra info.
There are also some more pessimistic estimates in sources that aren’t academic but do seem similarly worth paying attention to to Rees’ estimate; see my database.